Physical frailty is a growing problem in this country as the population of men and women over the age of 80 years is burgeoning. Physical frailty is a complex phenomenon with a number of factors associated with the condition including diminished strength, balance, flexibility, sensation, aerobic capacity and slowing of movements. Consistent with physical frailty is a loss of independence in performing fundamental activities of daily living and compromise in remaining function, particularly in the community. There is growing evidence that frailty is the consequence of inactivity and that exercise can modify the factors associated with the condition and, enhance functional capacity. There are, however, few guidelines for the application of exercise for the modification of physical frailty. While it is important to determine that exercise can reduce risk factors for frailty, it is also important to determine how exercise can improve physical capacity in frail adults. The goal of this project is to examine the efficacy of three different types of exercise as modifiers of physical frailty, in order to establish exercise and rehabilitation guidelines for clinical practitioners working with older, frail adults. It is also the intent of this project to determine the mechanisms responsible for positive change by examining the effect of each exercise mode on functional capacity and on the multiple risk factors associated with frailty. Specific aims include: 1. Compare the effects of three separate and specific exercise protocols on physical frailty: Flexibility/balance, Weight- training, Aerobic activity. 2. Identify the specific effects of each exercise mode on factors known to be associated with the development of physical frailty: diminished aerobic capacity, strength, range of motion, movement speed, and balance. 3. Determine if the gains from each exercise program can be sustained for 3 months.